The metabolism of aromatic acids by micro-organisms. Metabolic pathways in the fungi.
1. The metabolic pathways of aromatic-ring fission were examined in a range of fungal genera that utilize several compounds related to lignin. 2. Most of the genera, after growth on p-hydroxybenzoate, protocatechuate or compounds that are degraded to the latter (e.g. caffeate, ferulate or vanillate), rapidly oxidized these compounds, but not catechol. 3. Such genera possessed a protocatechuate 3,4-oxygenase and accumulated beta-carboxymuconate as the product of protocatechuate oxidation. This enzyme had a high pH optimum in most organisms; the Rhodotorula enzyme was competitively inhibited by catechol. 4. beta-Carboxymuconate was converted by all competent fungi into beta-carboxymuconolactone, which was isolated and characterized. None of the fungi produced or utilized at significant rates the corresponding bacterial intermediate gamma-carboxymuconolactone. 5. The lactonizing enzymes of Rhodotorula and Neurospora crassa had a pH optimum near 5.5 and approximate molecular weights of 19000 and 190000 respectively. 6. The fungi did not degrade the isomeric (+)-muconolactone, gamma-carboxymethylenebutanolide or beta-oxoadipate enol lactone at significant rates, and thus differ radically from bacteria, where beta-oxoadipate enol lactone is the precursor of beta-oxoadipate in all strains examined. 7. The end product of beta-carboxymuconolactone metabolism by extracts was beta-oxoadipate. 8. Evidence for a coenzyme A derivative of beta-oxoadipate was found during further metabolism of this keto acid. 9. A few anomalous fungi, after growth on p-hydroxybenzoate, had no protocatechuate 3,4-oxygenase, but possessed all the enzymes of the catechol pathway. Catechol was detected in the growth medium in one instance. 10. A strain of Penicillium sp. formed pyruvate but no beta-oxoadipate from protocatechuate, suggesting the existence also of a ;meta' type of ring cleavage among fungi.
D001203:Ascomycota / Q000201:enzymology / Q000378:metabolism; D001487:Basidiomycota / Q000201:enzymology / Q000378:metabolism; D001565:Benzoates / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism*; D002474:Cell-Free System; D005658:Fungi / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007783:Lactones / Q000378:metabolism; D003904:Mitosporic Fungi / Q000201:enzymology / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008954:Models, Biological; D008970:Molecular Weight; D009491:Neurospora / Q000201:enzymology / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism*; D010407:Penicillium / Q000201:enzymology / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors
D001565:Benzoates; D002396:Catechols; D007783:Lactones; D011773:Pyruvates; D006899:Mixed Function Oxygenases; D010105:Oxygenases